Effect of Cloud-Seeding on Water Stress of Maize

摘要

Results of experimental cloud-seeding in Zimbabwe are summarized, and indicate that silver iodide treatment enhances rainfall if cloud-tops are colder than -10C. Higher increases result if tops are colder than -13C. By comparing distribution functions fitted to seeded and to non-seeded clouds, tentative relationships were built up between natural and seeded rainfalls. A model was developed capable of simulating a cloud-seeding season in northeast Zimbabwe, whereby 1,000 showers were distributed at random within a rectangular area, enabling total extra rainfall to be computed at every km grid-point. Less than half the area received any additional rainfall. A soil water balance routine was then used to relate the apparently increased rainfall to changes in maize yield. In approximately half of all rainy seasons in northern Zimbabwe there appears to be adequate natural rainfall such that cloud-seeding is of negligible benefit to maize.